Thus the best experimental conditions of UV-A LED treatment were:
illuminator L30, V20 voltage, 0.5 cm distance from sample and
2.43 · 10−3 Wm−2 irradiance. Fig. 2 shows the ΔE of treated
(L30V20) and untreated (CL30V20) Golden Delicious apple slices as
function of exposure time. It is apparent that the standard deviation
was higher in CL30V20 and in the first time points of L30V20 as a
consequence of the variability in plant samples despite the maximum
standardization of the trial. The increase over time of ΔE values of
L30V20 treated samples (61% at 60 min) was less than that of
CL30V20 (75% at 60 min). Overall, the %RΔE of treated samples compared
to corresponding controls was 28% at 10 min, 49% at 30 min
and 53% at 60 min. It is clear that the anti-browning performance of
treatment was related to exposure time nearly all the reduction in
color change was seen already after 30 min